The first no-hitter in New York Mets history was costly: Baxter and Ramirez are headed to the disabled list, both injured on a memorable night at Citi Field. And manager Terry Collins remains concerned about Santana after the left-hander threw a career-high 134 pitches.

Baxter is expected to miss about six weeks after crashing into the left-field fence while making an outstanding catch to preserve Santana’s gem Friday night against St. Louis. Ramirez strained his right hamstring during the postgame celebration.

When it comes to the Mets, it seems, even big success comes with plenty of pain.

The team plans to place Baxter and Ramirez on the 15-day disabled list Sunday and bring in a couple of reinforcements.

The Mets said Saturday that Baxter displaced the joint between his right collarbone and sternum and tore rib cartilage on his right side when he slammed into the outfield fence to rob Yadier Molina of extra bases in the seventh inning. Baxter actually hit the padded wall with his left shoulder, and stayed down on the warning track because it went numb.

“It’s almost like a dislocation,” Collins said. “It’s not a fracture. The doctor said it could take up to six weeks to heal.”

Baxter described the timetable for his return as similar to that of Jason Bay, who has a broken rib and has been out since April 24. The left fielder is close to returning, perhaps in the coming week.

Ramirez was injured running onto the field with teammates to mob Santana after he finished the first no-hitter in the Mets‘ 51-season history.

“He was just running in,” Collins said. “He didn’t even get to the pile. He was running hard and all of a sudden his leg grabbed him.”

After all that, Santana came off the field after celebrating with his teammates and saw Collins waiting on the top step of the dugout. The two embraced and Santana said: “I told you to trust me.”

“I said, ‘Yeah you did,’” Collins said Saturday, still proud a day after Santana threw the first no-hitter in team history — a wait of 8,020 games.

Santana said his surgically repaired left shoulder felt fine even after all those pitches.

Collins said he was conflicted about leaving Santana in so long, but ultimately realized he was not going to deny the ace a chance at history. The former Astros and Angels skipper has only been with the Mets for two years, but he knew how much getting a no-hitter — finally, after all those seasons and excellent pitchers who have come and gone from Queens — would mean to the organization and its fans.

“He wasn’t coming out. I wasn’t going to take him out,” Collins said. “The fight that would have taken place on the mound had I taken him out would have been a bigger story than the no-hitter.”

If Santana winds up missing a start, it could dampen one of the finest moments in team history. Santana wasn’t thinking about that. Not with a no-hitter just a few outs away.

“When I had that situation there, I knew I had to take the most out of it. And then we’ll figure it out tomorrow,” Santana said. “Today I felt fine. Definitely, the next couple days are going to be important to see how I recover, and if we have to take an extra day, there’s nothing wrong with that.

“Terry and all the staff, they know what they’re doing. We’re going to do whatever’s best for all of us. If that means taking an extra day, there’s nothing wrong with that.”

When Collins went home Friday night, he said he was still hoping he made the right decision. He said he heard from general manager Sandy Alderson and chief operating officer Jeff Wilpon, among others.

“The general consensus was, ‘Don’t beat yourself down over this, you made the right move,’” Collins said. “I appreciate that. I appreciate their confidence in the move.”

Collins has been proactive about preventing injuries this season. In April, he learned that David Wright jammed a finger, and took him out of the lineup rather than let the star third baseman play through the pain and risk exacerbating it, or harming his production.

Wright missed three days and is off to a torrid start with an on-base percentage of .472, more walks than strikeouts, and, after going deep in Saturday’s 5-0 win, six home runs. Santana has waited an extra day between starts when the schedule and roster allowed, and Collins has limited his pitches. In a four-hit shutout of San Diego his previous time out, Santana needed only 96 pitches, though Collins said he would have pulled him after about 10-15 more.

Though pitch counts are mostly a guess at limiting fatigue, and some pitchers can tolerate more use than others, Collins was anxious. In the end, he just couldn’t bring himself to deny Santana his moment, even though he knew it was a risk.

“You take a major piece and all of a sudden he’s not there and he’s a big piece, you really struggle with, ‘Was it the right decision to make?’” And we won’t know for a couple days,” Collins said. “Sandy supported it, Jeff supported it. I got a tremendous call from Tony La Russa today, which I was appreciative of, saying, ‘Look, you did the right thing.’ So when it comes from those people, you feel a lot better about it.”

Whatever the cost winds up being, the Mets have their first no-hitter.

“My first reaction was, ‘Wow, they finally did it,’” Hall of Fame pitcher Tom Seaver said in a statement. “Honestly, not having a no-hitter was an anomaly. It’s great to get this off the franchise’s back. Now they can’t say the Mets are without a no-hitter.”

Another former Mets ace, Dwight Gooden, said he was flipping between an NBA playoff game and the Mets game, at least for a while.

“Once it got to the seventh inning, I was like, forget the Heat game,’” Gooden said. “I’ve always been a Met at heart.”

The absence of a no-hitter had dogged fans and the organization for years — the last several of which have been full of late-season collapses, injuries, trades and only recently, a little bit of promise from some young players who have contributed.

“It’s been a trying two years due to injuries and due to moves that have been made and we’re trying to establish some credibility, not just in the city but in major league baseball,” Collins said. “I think what happened last night gave us credentials.”